What coolant are people using in their hydronic systems? Ethylene glycol or propylene glycol? If it's ethylene glycol, how does one ensure this never gets in the freshwater system? If it's propylene glycol, how does one ensure this never gets in the engine coolant?
I'm referring to a "full Rixen" type system w/ hot water and engine connections when I ask this.
To answer my own question... I think a "backflow prevention assembly" is the key to keeping glycol and domestic drinking water separate (if the water heat hex fails, that is). I think if you're going to make the engine connection that one needs to switch to ethylene glycol to protect your engine, else stick w/ propylene glycol if you're just going to keep the loop separate. Something like this Zurn Wilkins offering or like this Watts offering